Method of recovering and recycling boron trifluoride catalyst

ABSTRACT

Spent boron trifluoride catalyst is removed from organic liquids by contacting the liquid with polyvinyl alcohol. For example, boron trifluoride catalyst is removed from 1-olefin oligomer product by passing the liquid oligomer through a bed of granular polyvinyl alcohol. The boron trifluoride is recovered from the polyvinyl alcohol and is recycled for use as a catalyst.

This is a division, of application Ser. No. 396,255 filed July 8, 1982,now U.S. Pat. No. 4,384,162.

SUMMARY OF THE INVENTION

Boron trifluoride which is present in minor amounts as a spent catalystin an organic liquid is removed from the organic liquid by contactingthe liquid with particulate polyvinly alcohol. The boron trifluoridecatalyst which is removed can be present in the organic liquid asdissolved boron trifluoride gas, or it can be coordinated with a polarcompound, or it can be present in both forms. The boron trifluoride isrecovered from the polyvinyl alcohol and is recycled for use as acatalyst.

DESCRIPTION OF THE INVENTION

Boron trifluoride is used as a catalyst in relatively small amounts inthe synthesis of a wide variety of liquid organic compounds, and inparticular liquid hydrocarbon compounds, including use as a catalyst inpolymerizations, in alkylations, in esterifications, and the like.Depending on the particular reaction being catalyzed, boron trifluoridecan be present in the reaction liquid either in the free state asdissolved boron trifluoride gas, or it can be in the form of acoordination compound. Additionally, it can be present in both forms, asa dissolved gas and also as part of a coordination compound. Once thecatalyzed reaction is completed, this minor amount of boron trifluoridemust be removed from the product organic liquid. But this removalpresents costly processing and disposal problems.

These problems can be exemplified by the process in current use for thepreparation of synthetic hydrocarbon functional fluids, such assynthetic lubricating oils, from higher 1-olefins, particularly1-decene. In the process, as described in U.S. Pat. No. 4,045,507 forone, the 1-decene is oligomerized to a product predominating in thetrimer and tetramer using a combination catalyst system comprising bothfree dissolved boron trifluoride gas and a coordination compound ofboron trifluoride and a suitable polar compound such as n-butanol. Theresulting oligomer product will contain both free dissolved borontrifluoride as well as the boron trifluoride coordination compound. Thisboron trifluoride must be removed from the oligomer product.

A typical processing scheme frequently recommended for eliminating borontrifluoride from the oligomer product includes the chemical destructionof the boron trifluoride by the addition of an aqueous caustic washstream. But this procedure involves the loss of the relatively expensiveboron trifluoride and further involves rather costly by-product handlingand disposal procedures to avoid environmental contamination. Theprocess also requires the removal of the introduced moisture from thehydrocarbon product. Furthermore, the n-butanol contaminant in theproduct must be separately removed and treated.

We have discovered a relatively inexpensive method for removing borontrifluoride, both the free, dissolved boron trifluoride and the borontrifluoride tied up in the coordination compound in an organic liquid.Our process is particularly beneficial, both for economical and forenvironmental reasons, because the separated boron trifluoride can berecycled for reuse in the process. As a result, both the borontrifluoride costs and the overall processing costs are substantiallyreduced. Additionally, any environmental problems currently resultingfrom catalyst by-product waste disposal are substantially eliminated.

Our invention comprises a hydrocarbon conversion process which utilizesboron trifluoride as a catalyst. In the process, a liquid hydrocarbon isreacted in the presence of boron trifluoride to form a liquid reactionproduct containing boron trifluoride. This liquid reaction product iscontacted with polyvinyl alcohol whereby the polyvinyl alcohol adsorbsthe boron trifluoride. The boron trifluoride is next desorbed from thepolyvinyl alcohol and is recovered and is then recycled to thehydrocarbon conversion stage.

When the boron trifluoride is used in the free state, that is, not as acoordination compound, it is dissolved in the reaction liquid generallyunder moderate pressure. When the boron trifluoride is used as acoordination compound, it can be coordinated with a suitable polarcompound in situ or it can be added to the reactor as the pre-reactedcoordination compound. When the reactor is pressured with borontrifluoride in the presence of the coordinating polar compound, bothdissolved, uncomplexed boron trifluoride and complexed boron trifluoridewill be present in the reaction liquid. Various polar compounds havebeen recommended as useful for forming coordination compounds with borontrifluoride for use as a catalyst. These include: aliphatic ethers, suchas dimethyl ether and diethyl ether; aliphatic alcohols, such asmethanol, ethanol, n-butanol and decanol; polyols, such as ethyleneglycol and glycerol; water; aliphatic carboxylic acids, such as aceticacid, propanoic acid and butyric acid; esters, such as ethyl acetate andmethyl propionate; ketones, such as acetone; aldehydes, such asacetaldehyde and benzaldehyde and acid anhydrides, such as acetic acidanhydride and succinic acid anhydride.

The product from the boron trifluoride-catalyzed process, whether batchor continuous, will contain a significant, albeit minor, amount of theboron trifluoride catalyst, free and/or coordinated, which must beremoved following reaction since it inherently contaminates the product.In general, it is desired that every product which is synthesized usingboron trifluoride catalyst be essentially free of this substance. Ingeneral, boron trifluoride contaminant can be effectively removed fromorganic liquids by our process when it is present in an amount as highas about five to ten weight percent. More generally, boron trifluoridecontaminant will be present in organic liquids in an amount between0.005 and about one percent.

When uncomplexed boron trifluoride is present in a liquid in significantamounts, white fuming usually results upon exposure of the contaminatedliquid to the atmosphere as the result of the reaction of the borontrifluoride vapors with atmospheric moisture. This fuming is a roughindicator of the presence of a significant quantity of undesired freeboron trifluoride dissolved in the liquid.

The polyvinyl alcohol which we use in our process for removal of theboron trifluoride is present in particulate form, generally within asize range of between about 10 mm and about 400 mesh, and preferablywithin a range of about 10 mm and about 100 mesh. It can be used in abatch purification procedure in which the particles of polyvinyl alcoholare dispersed throughout the liquid product by agitation until the borontrifluoride is adsorbed by the polyvinyl alcohol. However, it ispreferred to use a continuous separation procedure in which the reactionproduct is passed through a bed of granular polyvinyl alcohol. A cyclicoperation is possible in which one bed of polyvinyl alcohol adsorbent isregenerated while a second bed is removing boron trifluoride contaminantfrom the product stream. Since polyvinyl alcohol is generally preparedby the hydrolysis of polyvinyl acetate, some residual acetate may bepresent. We prefer polyvinyl alcohol which is at least 80 percenthydrolyzed, and more preferably which is at least 85 percent hydrolyzed.We most prefer fully hydrolyzed polyvinyl alcohol.

A particularly fortuitous and advantageous discovery by us was that thepolyvinyl alcohol removes not only free, dissolved boron trifluoridefrom the organic product liquid, but that it also removes borontrifluoride from its coordination compound with a polar compound,leaving the polar compound in the organic product liquid. Our data showsthat polyvinyl alcohol is an effective adsorbent up to its saturationpoint for both dissolved and complexed boron trifluoride.

Our process for removing boron trifluoride contaminant from organicliquids can be conveniently carried out at room temperature (20°-25° C.)or lower, such as 0° C. Since elevated temperatures prevent theadsorption of the boron trifluoride by the polyvinyl alcohol, atemperature of about 100° C. is generally not exceeded in the adsorptionprocess, and much lower temperatures are preferred.

In the adsorption process the organic liquid can suitably be passedthrough the bed of polyvinyl alcohol at a weight hourly space velocityin the range of about 0.1 to about 100 hr.⁻¹, preferably about 0.5 toabout 20 hr.⁻¹, and most preferably about 1 to about 5 hr.⁻¹.

When the polyvinyl alcohol adsorbent is saturated with borontrifluoride, it is taken out of service. Desirably, the borontrifluoride is recovered from this adsorbent by extracting it, and theboron trifluoride and the adsorbent are reused. In a convenientprocedure for the recovery of the boron trifluoride, the polyvinylalcohol is heated at a moderate temperature, such as about 100° C. at areduced pressure, to vaporize off the boron trifluoride. This recoveredboron trifluoride can then be directly reused in the process.Alternatively, the boron trifluoride can be stripped from the polyvinylalcohol adsorbent by contacting it with a polar compound. In thisstripping procedure, the concentration of the polar compound will behigh relative to the boron trifluoride. This recovery of borontrifluoride from the sorbent is possible because, it is believed, thedistribution of the boron trifluoride between the phases is governed byequilibrium. For process simplification, the polar compound used in thisrecovery stage is the same one used in the catalyticcoordination-compound catalyst.

It is also possible to coat a suitable solid support, such as silica,alumina, magnesia, zirconia, charcoal mixtures thereof such assilica-aluminas, and the like with polyvinyl alcohol for use as theadsorbent for boron trifluoride. This can be accomplished by contactingthe support with a hot aqueous solution of the polyvinyl alcohol. Theboron trifluoride can then be recovered from the saturated, supportedpolyvinyl alcohol for recycle. The regenerated supported polyvinylalcohol can be directly used, or, if desired, the polyvinyl alcohol canbe burned off and the support recoated with a fresh solution ofpolyvinyl alcohol for reuse.

DESCRIPTION OF PREFERRED EMBODIMENTS

DuPont Elvanol grade 70-05 polyvinyl alcohol was used in the followingexperiments. It was a low molecular weight, fully hydrolyzed (99-100percent) composition of 40/50 mesh size. A liquid synthetic hydrocarbonoligomer mixture was produced from 1-decene by the process described inU.S. Pat. No. 4,045,507 using a boron trifluoride-n-butanol complex in asystem pressured with boron trifluoride gas. The product mixture wastherefore contaminated both with free and with complexed borontrifluoride. The boron in the purified product was analyzed using anatomic adsorption technique.

EXAMPLE 1

The ability of polyvinyl alcohol to adsorb boron trifluoride from a gasmixture was determined. A 13.1 g. sample of the polyvinyl alcohol waspacked in a flow-through glass reactor. A gas mixture consisting of 100cc/minute of nitrogen and 20 cc/minute of boron trifluoride was flowedthrough the polyvinyl alcohol at atmospheric pressure and roomtemperature (20°-25° C.). After 230 minutes the gas flow was stopped,and the polyvinyl alcohol adsorbent was weighed. It was found that thepolyvinyl alcohol had adsorbed 16.4 g. of boron trifluoride, or 55.6percent by weight.

EXAMPLE 2

A flow-through glass reactor was packed with a bed of 1.28 g. of thepolyvinyl alcohol. Oligomer product contaminated with about 0.52 weightpercent boron trifluoride was allowed to trickle down through the bed ofadsorbent at a weight hourly space velocity of 11.5 hr.⁻¹ and at roomtemperature. Periodic cuts were collected about every thirty minutes,and some of these were analyzed for boron using atomic adsorptiontechniques. The boron trifluoride was almost quantitatively removeduntil the polyvinyl alcohol appeared to become saturated, at which pointadsorption essentially stopped. When this breakthrough of substantialquantities of boron trifluoride in the product occurred, a total ofabout 73 g. of contaminated oligomer product had been processed, and atotal of about 0.38 g. of boron trifluoride had been removed by thepolyvinyl alcohol. The results of this experiment are set out in TableI.

                  TABLE I                                                         ______________________________________                                                        Cumulative                                                                              B in cut,                                                                            Total B removed                              Cut No.                                                                              Wt., gms wt, gms.  ppm    mg. (est.)                                   ______________________________________                                        1      4.62      4.62     --      4.28                                        2      8.31     12.93     <10    11.18                                        5      8.59     38.24     22     31.96                                        7      7.31     53.25     18     44.32                                        9      6.77     67.08     28     55.82                                        10     6.24     73.32     --     61.08                                        12     5.55     84.80     700    61.08                                        ______________________________________                                    

Several of these purified product cuts were analyzed by gaschromatography to determine whether the product itself sufferedcompositional changes as a result of the polyvinyl alcohol adsorptionprocedure. It was determined that there was no significant effect on theproportion of the various oligomer fractions, beyond normal analyticalvariation, as indicated from the results of the analysis as set out (inweight percent) in Table II.

                  TABLE II                                                        ______________________________________                                                 C.sub.10                                                                             C.sub.20                                                                             C.sub.30 C.sub.40                                                                           C.sub.50.sup.+                           ______________________________________                                        Crude product                                                                            6.75     13.5   56.0   22.8 1.52                                   Cut No. 1  4.58     11.1   56.7   24.4 3.24                                   Cut No. 5  4.97     11.1   57.3   24.4 2.23                                   Cut No. 9  4.42     11.4   57.5   24.6 2.08                                   ______________________________________                                    

EXAMPLE 3

A 1.64 gm. quantity of the polyvinyl alcohol adsorbent was placed in aglass column to form a bed about one-half inch in diameter and 1.5inches high. The boron trifluoride-contaminated oligomer mixturecontaining 760 ppm of boron was pumped from a continuously stirredreactor through the adsorbent at a weight hourly space velocity of 46hr.⁻¹ and at a temperature of 20°-25° C. Samples of decontaminatedproduct were collected as before and were analyzed. The results,including the percent removal of the boron trifluoride, are shown inTable III.

                  TABLE III                                                       ______________________________________                                               Total amount B in treated                                                                              BF.sub.3 removed,                             Sample collected, gms                                                                             product, ppm                                                                              %                                             ______________________________________                                        1      14.76        <5          99.34                                         2      45.10        10          98.68                                         3      107.42       19          97.50                                         4      154.16       41          94.61                                         ______________________________________                                    

The polyvinyl alcohol adsorption procedure was continued until a totalof 185.3 gms. of the contaminated product were treated. Since thecontaminated product prior to the polyvinyl alcohol adsorption treatmentwas determined, by analysis, to contain 3,280 ppm n-butanol, the 185.3gms. of contaminated product, before treatment, contained 0.608 gm. ofn-butanol. The polyvinyl alcohol was analyzed after treatment, and only0.007 mg. of n-butanol was found on the polyvinyl alcohol.

In another experiment, a sample of polyvinyl alcohol adsorbent wassubjected to five cycles of adsorption and regeneration using n-butanol.It was determined that the four-times regenerated polyvinyl alcohol wasin effective adsorbent in the fifth cycle.

It is to be understood that the above disclosure is by way of specificexample and that numerous modifications and variations are available tothose of ordinary skill in the art without departing from the truespirit and scope of the invention.

What is claimed as the invention is:
 1. A boron trifluoride-catalyzedchemical reaction which comprises the steps:(1) converting an organicreactant to an organic reaction product in a liquid-phase chemicalreaction in the presence of boron trifluoride catalyst whereby aliquid-phase product solution is obtained containing said borontrifluoride; (2) contacting said liquid-phase product solution with aparticulate polyvinyl alcohol composition whereby said boron trifluorideis adsorbed by the polyvinyl alcohol; (3) desorbing the borontrifluoride from the polyvinyl alcohol; and (4) recycling the desorbedboron trifluoride to the liquid-phase chemical reaction for further useas a catalyst.
 2. A boron trifluoride-catalyzed chemical reaction inaccordance with claim 1 in which the boron trifluoride catalystcomprises free dissolved boron trifluoride.
 3. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the boron trifluoride catalyst comprises a coordination compoundof boron trifluoride and an organic polar compound.
 4. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the boron trifluoride catalyst comprises a coordination compoundof boron trifluoride and water.
 5. A boron trifluoride-catalyzedchemical reaction in accordance with claim 1 in which the polyvinylalcohol is at least about 80 percent hydrolyzed.
 6. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the polyvinyl alcohol is of a particle size between about 400 meshand about 10 mm.
 7. A boron trifluoride-catalyzed chemical reaction inaccordance with claim 1 in which said liquid-phase product solution iscontacted with said particulate polyvinyl alcohol composition at atemperature between about 0° C. and about 100° C.
 8. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the polyvinyl alcohol is substantially fully hydrolyzed.
 9. Aboron trifluoride-catalyzed chemical reaction in accordance with claim 1in which said liquid-phase product solution is substantially completelyfreed of boron trifluoride by adsorption of the boron trifluoride onsaid polyvinyl alcohol composition.
 10. A boron trifluoride-catalyzedchemical reaction in accordance with claim 1 in which the borontrifluoride is desorbed from the said polyvinyl alcohol composition bycontacting the polyvinyl alcohol composition with an organic polarcompound whereby said boron trifluoride is desorbed and a coordinationcompound of said desorbed boron trifluoride and said organic polarcompound is produced, and said coordination compound produced by thedesorption procedure is recycled to the liquid-phase chemical reactionfor use as a catalyst.
 11. A boron trifluoride-catalyzed chemicalreaction in accordance with claim 10 in which said organic polarcompound is an alkyl alcohol having from one to about ten carbon atoms.12. A boron trifluoride-catalyzed chemical reaction in accordance withclaim 11 in which said organic polar compound is n-butanol.
 13. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the said organic reactant comprises a liquid hydrocarbon.
 14. Aboron trifluoride-catalyzed chemical reaction in accordance with claim13 in which the said organic reactant comprises a liquid 1-olefin.
 15. Aboron trifluoride-catalyzed chemical reaction in accordance with claim14 in which said organic reactant comprises 1-decene.
 16. A borontrifluoride-catalyzed chemical reaction in accordance with claim 11 inwhich the said organic reactant comprises a liquid 1-olefin.
 17. A borontrifluoride-catalyzed chemical reaction in accordance with claim 1 inwhich the boron trifluoride is desorbed from the said polyvinyl alcoholcomposition by vaporizing the boron trifluoride from the polyvinylalcohol composition at a moderately elevated temperature.
 18. Ahydrocarbon conversion process which utilizes boron trifluoride as acatalyst which comprises the steps, reacting a liquid hydrocarbon in thepresence of boron trifluoride to form a liquid reaction productcontaining boron trifluoride, contacting the reaction product withpolyvinyl alcohol whereby said boron trifluoride is adsorbed by thepolyvinyl alcohol, desorbing the boron trifluoride from said polyvinylalcohol, and recycling the recovered boron trifluoride to thehydrocarbon conversion stage.